Genetische Variation bei Wildpflanzen: Einfluss der fragmentation auf populationen von Succisa pratensis

The populations of many species of fens have been reduced to small relicts in consequence of agriculture and drainage. The populations often consist of a reduced number of individuals and they are geographically isolated from each other. This circumstance has been evident in the examined area for about 80-90 years. In this investigation Succisa pratensis was taken as example to test possible effects of habitat fragmentation on genetic diversity. Furthermore we investigated the relationship of the genetic diversity between a five year old population of Succisa pratensis, established by seeds and out-planting, and the source population in which the seeds were collected. The genetic diversity of seven populations was analysed by starch gel electrophoresis. Nine enzyme systems were studied which putatively encode for 12 poplymorphic gene loci. The total genetic diversity is H(T) = 0,315 and the diversity between populations is G(ST) = 0,120. There was no correspondence between population size and genetic diversity or heterozygosity. Even a small population of only about 120 individuals did not show lower genetic diversity than a population with several thousands of individuals. Genetic distances between populations did not correspond with geographic distances, although local patterns of genetic distance are evident. The genetic diversity of the restored population was as high as the diversity of the source population and both populations showed high genetic similarity. These results emphasize the significance of smaller relict populations of poor fens as a genetic reservoir for restoration measurements.